This disclosure relates to a device that prevents separation and more particularly to a portable wireless monitoring device that causes an indication when a pre-determined distance has been exceeded between two or more persons or objects.
Devices to prevent physical separation between persons and/or objects are known in the art. Although their applications vary, for example, preventing physical separation of an elderly person from their caregiver, preventing physical separation of an object from its owner, etc., devices that prevent physical separation of a child from his/her parent or caregiver have been in use for many years. For example, in the 1980's child tethering devices were not an uncommon sight at the local shopping mall. While effective for short distances, the child tethering devices were cumbersome, easily tangled and overall, visually unsettling.
Today, various electronic devices in one of many configurations have replaced the traditional child tethering devices of the past with electronic monitoring devices and monitoring device networks. For example, monitoring device networks that utilize a fixed base apparatus to prevent separation are known in the art. U.S. Pat. Nos. 4,593,273 and 4,675,656, to Narcisse entitled “Out-of-Range Personnel Monitor and Alarm,” disclose an out-of-range monitor and alarm system that utilizes a fixed base unit and at least one mobile unit. Similarly, U.S. Pat. No. 6,720,881 to Halliday, entitled “Perimeter Security Systems”, discloses a perimeter securing system for providing a security alarm for persons leaving or entering a predetermined area. The security system includes a main sensor wearable by a user, a perimeter defining assembly for providing an indication of a predefined area, and a remote unit for receiving a signal from the main sensor indicating that the boundary of the predefined area has been broken. Fixed base monitoring devices to prevent separation, however, do not lend themselves to mobile applications involving monitoring children on the move.
Mobile monitoring device networks that utilize mobile devices to prevent separation are known in the art. For example, U.S. Pat. No. 5,119,072 to Hemingway, entitled “Apparatus for Monitoring Child Activity”, discloses an apparatus that includes a mobile child transmitter with a voice encoder, a microphone, an oscillator and an antenna, and a mobile parent receiver. The oscillator frequency modulates a radio frequency (RF) carrier signal which is then transmitted from the antenna. The parent receiver unit includes circuitry for separating the audio and carrier components of the signal received from the child transmitter, and for comparing field strength of the carrier component to a range threshold. The audio component is fed into a speaker of the parent receiver for child activity monitoring purposes. When the amplitude of the carrier component drops below a threshold, an alarm is sounded on the parent receiver indicating that the child unit is out of the desired range.
U.S. Pat. No. 5,646,593 to Hughes et al, entitled “Child Proximity Detector”, discloses a child proximity detection network that includes two transceivers (transmitter/receiver) rather than a child transmitter and a parent receiver of the Hemingway patent. The 1st transceiver unit (parent transceiver unit) includes a parent identification number and the 2nd transceiver (child transceiver unit) unit includes a child identification number, assigned only upon physical connection with the 1st transceiver. During operation, the parent transceiver unit produces and transmits a polling message (including parent ID) to the child transceiver unit to determine if the child transceiver unit is further than a predetermined distance. Upon receipt, the child transceiver unit which “investigates” the polling message contact for matching with predetermined criteria and returns response if matched, and detects whether parent transceiver unit is more than a predetermined distance. Alarms sound if either detects other beyond the predetermined distance.
U.S. Pat. No. 5,661,460 to Sallen et al., entitled “Distance Determination and Alarm System”, discloses a monitoring device network that includes at least two transceivers such as a parent unit and a child unit for generating one alarm when the child unit is more than a predetermined distance away from the parent unit. Unlike similar designs where the distance is based on signal strength, the distance of the parent and child unit of the Sallen et al. patent is determined by a phase relationship of a reference signal from the time it is transmitted on an RF signal by the parent unit, received and retransmitted by the child unit, and then received again by the parent unit.
In some cases, a direction-finding feature is added to the mobile monitoring device network. For example, U.S. Pat. No. 6,127,931 to Mohr, entitled “Device for Monitoring the Movement of a Person”, discloses a homing unit (child unit) for generating and omitting a homing signal at predetermined intervals, and a base unit (parent unit) having a receiver for receiving the homing signal and a processor for processing homing signal strength and time of receipt between homing signals to determine whether the homing unit is within a predetermined distance. In addition to an alarm, the base unit includes a display for displaying the distance and direction between the base and homing unit. Similarly, U.S. patent application Publication, 2002/0046658 to Turner et al. entitled “Dual Watch Sensors to Monitor Children” and having a publication date of Mar. 11, 2004, includes a display on the caregiver or parent unit that displays which child transceiver is out of range as well as other visual indications of distances of child transceivers.
In other cases, one or more elements of the child unit are controlled by the parent unit. For example, U.S. Pat. No. 6,078,260 to Desch entitled “Method and Apparatus for Keeping Track of Children” discloses a system for monitoring the proximity and location of a child (having a child transceiver unit) by a parent (having a parent transceiver unit). In addition to a directional indicator, the parent transceiver unit includes a power switch which controls powering of both child and parent transceiver units and which when activated causes the parent transceiver unit to transmit a signal to activate the child transceiver unit. Similarly, in U.S. Pat. No. 5,939,988 to Neyhart, entitled “Child Proximity Monitor and Alarm”, an alarm included in the child transceiver unit is only deactivated via a deactivation signal from the parent unit. Likewise, U.S. Pat. No. 6,542,080 to Page, entitled “Monitoring Device to Prevent Separation”, discloses a wearable transmitter portion for the monitored child and a wearable receiver portion for the monitoring parent. The receiver portion includes a predetermined separation parameter, a means for determining distance between, an alarm and a reset button for turning off the receiver portion alarm and for resetting the alarm. The transmitter portion also has an alarm, however it can only be turned off by the receiver portion.
More advanced mobile monitoring devices that include GPS systems are also known in the art. U.S. Pat. No. 5,900,817 entitled “Child Monitoring System” to Olmassakian, and U.S. Pat. No. 6,570,504 and U.S. Published patent application US 2002/0080036 to Rabanne et al, entitled “System for Tracking Possessions” disclose mobile monitoring devices that indicate not only that a child or possession has moved beyond a pre-determined maximum distance limit but also indicate a distance and direction via an GPS assembly included in the monitoring devices.